1. Field of the Invention
The invention relates to a method of improving the adhesion properties of a non-oxide ceramic substrate before gluing it. The method according to the invention applies in particular to preparing ceramic substrates that support power semiconductor components and are to be glued to a cooling manifold to be used in inverters used in the railroad art.
2. Description of the Prior Art
Gluing an aluminum nitride (AlN) substrate supporting power components to a cooling manifold is known in the inverter art and usually includes a step of preparing the surfaces to be glued by cleaning the surfaces using chemical, mechanical or thermal methods. For the most recent assembly methods, the surfaces are cleaned by a method using a cold plasma consisting of a mixture of argon and oxygen. This method, which can be used in a white room environment, nevertheless has the disadvantage of necessitating a vacuum enclosure, which makes it time-consuming and complicated.
Also, the cleaning methods used until now generally pollute the power components that are placed on the ceramic substrate and the glued ceramic/polymer bonds obtained are very weak from the chemical point of view, moisture migrating easily at the interfaces, especially as the chemically or mechanically cleaned surfaces, which were inherently hydrophobic before treatment, become hydrophilic after treatment. As a result of this the glued joints obtained are not reliable in a hot and moist environment, as encountered by inverters in the railroad art.
Also, one object of the present invention is to propose a method of improving the adhesion properties of a non-oxide ceramic substrate before gluing it in order to ensure high-strength glued joints and high reliability in time, without polluting any power components present on the substrate, which method is simple and economic to put into practice.